The present invention relates to a metal-can label which is bonded to a metal can by heating adhesion and to a metal can carrying the metal-can label. Specifically, the present invention relates to a metal-can label that is resistant to peeling-off even when a metal can carrying the label undergoes, for example, drawing or retorting, and to a metal can carrying this metal-can label.
Metal cans include beverage cans that are filled with beverages such as soft drinks and beer, and spray cans that are filled with gases. These metal cans are classified as a three-piece can composed of a can body, a can bottom and a can lid, and a two-piece can composed of a can bottom and a can body formed as an integral can main body and a can lid fitted onto the can main body. In some cans, the neck of such a can main body is subjected to neck-in processing to form plural steps, and this type of cans have been used in large numbers in recent years.
When an external ornament such as a trade name, a manufacturer name, and a design (pattern) is made on a metal can such as a two-piece can or a three-piece can, the external ornament is generally printed directly onto the outer surface of the body of can main body. However, the outer surface of the body of metal can (two-piece can) to be printed generally curves cylindrically and is lower in printability than a conventional film printing, and a beautiful finishing cannot be significantly obtained. Particularly, color printing such as photomechanical printing which requires precise processes invites many problems, and there is a limitation when a satisfactory external ornament is to be made on a metal can by direct printing on the outer surface of the can body.
Consequently, an attempt has been made to yield an improved ornament by allowing the body of a metal can to carry a shrink label. However, shrinkage of the shrink label becomes uneven in, for example, neck-in processed portions, to invite deformation or rupture in the top edge or bottom edge of the shrink label, and the shrink label peels off from the metal can. Additionally, the shrink label is not bonded to the body surface of metal can, and when the shrink label reaches the rolled portion, the shrink label which is not bonded disadvantageously weakens the rolling strength.
Under these circumstances, as a metal-can label that can yield satisfactory external ornament, adhesive label 21 as shown in FIG. 9 has been discussed. Adhesive label 21 includes transparent label substrate 22, and print layer (or deposited metal layer) 23 and adhesive layer 24 composed of a thermosetting resin successively laminated on transparent label substrate 22. FIG. 10 is a sectional view showing the top of can main body 10. In this state, a metal can carrying aforementioned adhesive label 21 on its can body has been further subjected to neck-in processing. Adhesive label 21 can be surely affixed to the surface of the can body of metal can by heating adhesion, and does not deteriorate the rolling strength even when the adhesive label reaches the rolled portion. However, if the neck of the can body is subjected to extreme drawing (neck-in processing), stress is applied to attached label 21 in neck-in processed portion 10c, and the it top edge of the label peels off, as shown in FIG. 10. This peeling-off is generally occurs in the interface between print layer (or deposited metal layer) 23 and adhesive layer 24. Additionally, when the metal can carrying label 21 is subjected to hot water treatment or retorting, water or moisture enters the edge of label to invite the label to peel off.
Accordingly, an object of the present invention is to provide a metal-can label that can bear a satisfactory external ornament, can be surely affixed to the outer surface of the body of a metal can, and is resistant to peeling-off even when the metal can is subjected to extreme drawing or to hot water treatment or retorting, as well as to provide a metal can carrying the metal-can label.
After intensive investigations to achieve the above objects, the present inventors found that the formation of a clear portion having neither print layer nor deposited metal layer at the edge of a label make the label to be resistant to peeling-off even when a metal can carrying the label is subjected to extreme drawing or to retorting. The present invention has been accomplished based on these findings.
Specifically, the present invention provides a metal-can label to be bonded to a metal can by heating. The label includes a thermally stable transparent label substrate, an adhesive layer composed of a thermosetting resin, and at least one layer selected from a print layer and a deposited metal layer each formed between the transparent label layer and the adhesive layer, and the label has, at its edge, a clear portion having a predetermined width, in which the transparent label substrate and the adhesive layer are laminated without the interposition of any of the print layer and the deposited metal layer. In this label, the transparent label substrate may be made of a biaxially oriented polyester-based resin film, and the adhesive layer may be made of a thermosetting polyester-based resin.
In another aspect, the present invention provides a metal can which carries the metal-can label on the outer surface of a can body by action of heating adhesion. The metal can carrying the metal-can label on the outer surface of a can body by action of heating adhesion may be further subjected to neck-in processing. The metal can may carry the metal-can label on the outer surface of the can body in such a manner that the clear portion of the label is hidden by a rolled portion of the top of the can body and a can lid.